Starch manufacturing process



A. PELTZER V STARCH MANUFACTURING PRocfiss June 29, 1943.

Original Filed Jan. 14, 1933 8 Sheets-Sheet 1 ATTORNEY June 29, 1943. A.PEL'riER V STARCH MANUFACTURING PROCESS Original Filed Jan. 14, 1933 8Sheets-Sheet 2 ATTORNEY June 29, 1843.

A. PELTZE R STARCB IANU'FACTURING PROCESS Origingl Filed Jgmi. '14, 1953s Sheets-Sheet s 8 Sheets-Sheet 4 w IIQVENTOR 4/berf Rs-/f;cr

ATTORNEY v A. PELTZER STARCH MANUFACTURING PROCESS Original Filed Jan.14, 1933 June 29, 1943.

June 29, 1943.

A. PELTZER STARCH MANUFACTURING PROCESS Original Filed Jan. 14, 1933iCarr;

J44 3/0 5feeps '8 Sheets-Sheet 5 FIE E Tape/75' Mash wafer 3/0 .ifeeps I365 INVEN'i'O ATTORNEY June 29, 1943. r PELTZER 2,323,077

STARGH MANUFACTURING PROCESS Original Filed Jan. 14, 1935 8 Sheets-Sheet6 1 fine sla 393 377 392 fies/v lu Org side ATfoRN EY June 29, 1943. A.PELTZER 2,323,077

. Y STARCH MANUFACTURING PROCESS Original Filed Jan. '14, 1953 8Sheets-Sheet '7 Carry,

jfeaps 75/03 5 67:.) and in: $/o O 6/0/6/7 an fibe s/op INVENTORATTORNEY June 29, 1943. PELTZER 2,323,077

STARCH MANUFACTURING PROCESS Original Filed Jan. 14, 1955 8 Sheets-Sheet8 Corn 3/0- 5/ h... Tow/7s 4/ l 4/7 4 Q ,45/ Ger/:5 filfs s/em IC;O570,0 sys/g L flop R 4/9 fi/fer 436* 52/6,

FIE J l= INVEINTOR ATTORNEY Patented June. 29, 1943 s'rsncnMANUFACTURING rnocnss Albert mm. San Francisco, Calii'., assignor toMerco Centrifugal (30., San Francisco, Calif., a corporation ofCalifornia Continuationof applications Serial No. 651,701,

January 14, 1933, and Serial No. 741,528, September 11, 1934.

This application November 5, 1942, Serial No. 464.632

48 Claims. (Cl. 127-68) This invention relates generally to thecommercial manufacture of starch from starch hearing materials, likeIndian corn.

It is an object of the invention to provide a process and system for themanufacture of starch which will be relatively eflicient, particularlywith respect to'the yield of starch and the amount of water required.

It is a furtherpbject of the invention to provide a process and systemof starch manufacture which will require only a small number of silkscreens or reels, compared to prior practice, and which will utilizesuch screens or reels in a more effective manner.

. Another object of the invention'is to provide a system which will useonly comparatively fresh water in the milling process, and which willparticularly avoid the reuse of water which has passed through glutensettling operations.

A further object of the invention is to provide a process and systemwhich will dispense entirely with conventional tabling of mill starch toseparate starch from the gluten. In this connection the invention ischaracterized by the use of centrifuging, which is preferably appliedbefore treatment with silk screens or reels to remove fine fiber(conventionally known as fine slop). Centrifuging is also employed towash the starch, thereby enabling manufacture of products of greatpurity.

A further object of the invention is to provide a novel process usingcentrifuging for primary separation between starch and gluten, withsimultaneous displacement of solubles into the overflow, and with novelutilization and distria wet starch process having a novel procedure forobtaining relatively clarified process liquor for reuse in the system,the procedure involving special treatment of the overflow from acentriiuging operation being supplied with a starchgluten magma forprimary separation.

A further object of the invention is to provide a process involving animproved procedure for the handling of grits, which is characterized bydirect centrifuging of a magma containing finely divided starch, starchgrits, and gluten.

A further object is to provide a novel procedure making it possible todraw on a comparatively heavy grit starch without employing conventional thickening equipment.

Further objects of the invention will appear from the followingdescription in which the preferred embodiments of the invention havebeen set forth in detail in conjunction with the accompanyingdrawings.

Referring to the drawings:

Fig. 1 is a diagrammatic flow sheet illustrating a system for themanufacture of starch, incorporating the present invention.

Fig. 2 is likewise a flow sheet illustrating a vention;

bution of process liquors derived from the gluten overflow andv thestarch underfiow.

Another object of the invention is to provide a novel process utilizingcentrifuges and having provision for supplying starch containing magmasof proper gravity for the centrifuge operation or operations.

'Another object of the invention is to provide a novel centrifugingprocess or method making use of a counter-flow series of centrifugestages, the process being characterized by economical wash waterrequirements and effective separation of the desired solid componentslike starch, from contaminants like gluten and so-called solubles.

Another object of the invention is to provide a. novel centrifugeprocess or method making use of a counterilow series of centrifugestages for the separation of various solids from magmas containingsolids in suspension.

A further object of the invention is to provide Fig. 3 is a sideelevational view, in transverse cross section, illustrating a centrifugewhich can be utilized in the systems of Figs. 1 and 2.

Fig. 4 is a cross sectional detail, illustrating valve means forwithdrawing a controlled amount of underflow from the centrifuge of Fig.3.

Fig. 5 is a cross sectional detail, illustrating the.

nature of certain parts of the system shown in Figs. 1 and 2.

Fig. 7 is a diagrammatic view illustrating the manner in whichthecentrifuge of Fig. 3 opertrifuged.

Fig. 9 illustrates another embodiment of the invention differing fromFig. 8 particularly with respect to use of centrifuges for primaryseparation in place of tabling.

Fig. 10 illustrates a simplified embodiment of the invention in which asingle stage of centrifugal treatment carries out primary separation ona combined mill starch stream containing fine slop. I Fig. 11illustrates another embodiment of the invention differing from Fig.particularly in that grits are carried in the mill starch stream beingfed to the centrifuging operation. I

Fig. 12 illustrates another embodiment of the invention differing from.Fig. 11 particularly in that two centrifuges are arranged in series withsilk or fine screening interposed between the two stages.

Fig. 13 illustrates a further embodiment of the invention differing fromFig. 12 particularly in that the combined mill starch stream issubjected to filtering and repulping to provide a relatively highgravity magma for feeding the first centrifuge stage.

Fig. 14 represents another embodiment of the invention in which gritstarch and Buhr mill starch are separately centrifuged.

Before explaining my process and system, it should be noted that certainarbitrary conventions have been followed in the flow sheets of Figs. 1and 2. Thus a dotted line has been used to indicate the main starchflow. Double solid lines, that is two lines in close parallelism,-indicate the main gluten flow. Dot-dash lines indicate the main germflow; double dot-dash lines the main coarse slop flow; and single solidlines indicate auxiliary flow.

In common withprocesses of the prior art, in this invention the corn isfirst disintegrated to permit separation of certain components forfurther treatment; Thus referring to the flow sheet of Fig. 1, line 8represents introduction of corn to the steeping system or apparatu 9.Line |8 represents a steep water overflow, while lin I representsintroduction of sulphur dioxide. Line |2 represents introduction ofsteeped corn from 8 to the degerminator or cracking mill I3.

The next step of the process is to remove germs from the disintegratedcorn. Thus I have shown a plurality of germ separators l4, l6 and H, thedisintegrated corn being delivered to the first separator M by line |8.Line 28 indicates removal of the germs from the'separators l4, l6 andI1. Removal of that component containing the bran with some of thestarch, from separator I4, is represented by lin 19. This component istreated by a grind reel 2|, to remove bran, and the coarser materialfrom the grind reel 2| is then treated in a further cracking mill ordegerminator 22. Cracked material from degerminator 22 is shown beingdelivered to the second germ separator l6.

The third or auxiliary germ separator makes available a grit starch fromwhich a certain amount of the'desired starch can be immediatelyseparated, before further treatment with a Buhr mill. In conjunctionwith the auxiliary germ separator I1, I employ a second grind reel 23,which is fed from a mixer box 24. Mixer box 24 receives material fromthe outflow side of degerminator 22, and also a certain part of thefiner or screened material from the grind reel 2|. The remainder of thefiner material from grind reel 2|, is shown being delivered into alaunder 25, from which a flow occurs to the germ separator l6. Launder26 also receives the coarser components from the grind reel 23, wh le thfiner component from this reel is delivered to the auxiliary germseparator IT, for recovery of small particles of germ. With such anarrangement, the grit starch made available fro-m the germ separatorwill contain a considerable quantity of finely divided starch particleswhich can be removed with advantage before the material is treated in aBuhr mill, and likewise this grit starch will be substantially free ofbran. The removal of this grit starch from germ separator H has beenindicated'by line 28.

Removal of the separated starch bearing component from separator l8, hasbeen indicated by line 28, and is treated m a grind reel 3|. Line 32indicate removal of a grit starch (carrying the unground material) fromthis reel for further treatment, while line 33 indicates removal of a'separator, and grind reels, such as explained above, it is possible byproper control to have thegrit starch drawn on by way of line 28 at arelatively higher gravity than the grit starch as drawn off inconventional processes. In conventional processes the grit starch isdrawn on from the bottom discharge. of the germ separators. Suchoperation makes for best efliciency, because I prefer to immediatelysubject the grit'starch removed by way of line 28 to centrifugalseparation, before treatment of th same in a Buhr mill or like grindingapparatus. Since the hulls have been removed from material introducedinto separator ILsmall particles of germ can be recovered and gritstarch can be drawn oil at a materially higher gravity thap would bepossible in a germ separator where hulls or bran are present.

.Thecomponent removed as an overflow from the germ separators l4, l6 andI! by way of line the separated germflow from the first reel '38 feedingthe second reel 31, and the germ flow from the second reel 31 feedingthe third reel 38. The separated germ flow from reel 38 is supplied toan expeller 39, where excess water is removed. Water or washliquor'can'be supplied at various points in this system, as for examplethe water expelled at 39 can be returned to the feed of germ reel 31, byline -4|. The flow from reel 38, from which the germs have beenseparated, can likewise be returned to the feed of reel 31, as indicatedby line 42. Similarly the filtrate from reel 31 can be'introducedtogether 46. Thus one part of the filtrate returned by way of line 46 isshown being introduced into the germ separator l4 together with the feedfrom line l8, another part is shown being introduced together with thefeed to the degerminator or disintegrator |3, and another part into thelaunder 28 which in turn feeds germ separator l6.

Thus far I have disclosed that portion of my process and system whicheffects disintegration or degermination of the corn, and removal ofstarch from the-disintegrated corn to form grit starch for furthertreatment. I'shall now describe that portion of my process and systemfor further treatment of the grits and the other components in need ofgrinding. These components, removed by way of line 32, are shown beingtreated .in a suitable mill 5|, such as a Buhr mill, where theyare-finely ground. To remove coarse slop from the'materIal-discharge'dfrom Buhr mill I, and material taken from other parts of the p w... eshown a plurality of slop reel; 82, I8, 44 II. Buhr mill II feeds theBuhr slop reel 42, 'ancLthe filtrate from this reel, represented by linedorms a mill starch 'for further treatment. The

of line 83. After grits have been removed from the underflow ofcentrifuge I the liquor is introduced as feed material to centrifuge 8,as indicated by line 84. The Buhr, mill starch represented by flow line56, serves to feed the centrifuge 2, the gluten overflow from which,repre- SIOD, containing principally co fibrous rial, separated out byreel 42, feeds reel 43. Similarly reel 83 feeds reel 84, and thi latterreel feeds the reel 88. A couni'erflow effect is secured by. having thefiltrate from reel 83 returned together with the feed to reel 84. asindicated by line 81. likewise line 88 indicates return of filtrate fromreel 84 to reel 88. Line 88 also indicates return of filtrate from reel83 to the feed to reel 52. The material [separated out in reel 88 isdelivered to an expeller II, and the filtrate from this expeller isreturned to the feed to reel 84, as indicated by line 82. V

It has been previously stated that in effecting separation of the starchfrom gluten, I preferably utilize centrifuges in place of conventionaltabling. The centrifuge utilized should be capabl of continuousoperation without clogging, and should be capable of efficientlyseparating the desired starch. In this connection I prefer to utilizecentrifuges of the general type .disclosed and claimed in certaincopending applications, particularly application Serial No. 586,773, newPatent No. 2,013,668, and which is characterized by return of a part ofthe underflow back into the centrifuge chamber. A suitable centrifuge ofthis type will be presently described in detail. Referring again'to theflow sheet of Fig. l, the centrifuges illustrated have been numbered Ito 4 inclusive. Each of these centrifuges is shown provided with areturn circuit identified by letter A which serves to return a part ofthe heavier underflow back into the centrifuge chamber. The feed tocentrifuge I is the relatively high gravity grit starch, from line 28. Ashaker 86 may be imposed in this flow line, to remove stray oversizeparticles. The overflow from centrifuge I, which consists largely ofgluten, is shown being removed by way of line 61 and is delivered to aseparator 68. From separator 98, the gluten is delivered by line 89, toa settler II. The thickened material from settler II is treated in afilter press I2, where excess water is removed to recover gluten andfine slop. The overflow from settler II, together with the water removedin the filter press 12, is returned to the steep system 9. With respectto the other components separated out at 68, one component is treated bya silk shaker I3, and the filtrate from this shaker introduced togetherwith the feed to the germ reel 31, by way of line I4, and the othercomponent (a relatively clear liquor) is introduced into the gluten flowline 69, by way of line I6, together withthe material separated out bysilk shaker I3. As will be presently explained, introduction of filtrateby way of line 14 to the germ reel 31. serves to compensate for anexcess flow of water to centrifuges I and 2 and to regulate the gravityof gr. t starch to the first centrifuge.

The starch underflow from centrifuge I, represented by line I8, istreated by one or more silk shakers I9 to remove grits, and the grits soremoved are shown introduced by way of line 8!, to a second Buhr mill82. The finely ground material from Buhr mill 82 is shown beingintroduced into the Buhr mill starch line 56, by way sented'by line 86and containing a large amount of fine slop, is introduced into thesettler II together with the gluten fiow from centrifuge I. The feedtothe centrifuge 2 may likewise be treated' by a shakemscreen 81, toremove any stray oversize particles. 'Ehe underflow from centrifuge 2,represented by line 88 is likewise treated by one or more silk shakers89-to remove the fiber or residual slop content of thesame, hereinafterreferred to as small size coarse slop, and the material passing throughthis shaker screen is likewise merged with flow line 84 to form a feedfor centrifuge 3.

Centrifuges i and 2 perform mainly a. separating function, that is toseparate starch from product of high purity. The overflow fromcentrifuge 3 is represented by line 9|, and the starch underflow by line92. The starch underflow from centrifuge 3 is fed into centrifuge 4, theoverflow from which is represented by line 93. The starch underflow fromcentrifuge 4 represented by line 94, may be treated by one or more silkshakers 96, of the type commonly known as proving shakers, and thematerial passing through these shakers is then delivered to a filtersystem 91 for removing water from the finished product.

In the operation of my process it is necessary to introduce a certainamount of fresh water into the system. Thus introduction of fresh waterhas been indicated by way of line IIII. This fresh water is made up fromone component I02 at ordinary temperature, which may contain a suitablechemical to control hydrogen ion concentration of the starch, andanother component I83 at an elevated temperature and which may be a hotcondensate. A part of this water is introduced into the return circuitof centrifuge 4, and another part into the filter system 91.

- The various centrifuges arealso connected in counterflow relationshipwith respect to each other. Thus line I04 indicates introduction offiltrate from the filter system 91, into the return circuit ofcentrifuge 3. Line I06, together with line It", indicates introductionof overflow from centrifuge 4, into the return circuits of centrifuges Iand 2. In order to secure an excess of water in the overflows ofcentrifuges I and 2, and to compensate for an excess flow of wash liquorto centrifuge 3, line I88 indicates introduction of a part of theoverflow from centrifuge 3, into the overflow line I86 from centrifuge4. Likewise to secure an excess of water in the overflow from centrifuge3 and to compensate for excess flow of wash liquor to centrifuge 4, lineI89 represents diversion of flow from line 93, to line I 84. Similarlyto secure an excess of water in the overflow from centrifuge 4, line I II indicates diversion of flow from line I84 to the fresh water line IIlIleading to centrifuge 4. It will be presently explained that with thetype of centrifuge illustrated, sufficient wash liquor is provided sothat apart of the water introduced with the return flows continuallythrough the "zone of separation, to be discharged with the overflowwithout dilution of the underflow.

flow from centrifuges I and 2.

Liquor and other material removed at various points from the centrifugesystem can be utilized with advantage in other parts of the process.Thus I have shown the overflow liquor from line 9|, being diverted totwo portions, one portion flowing by way of line H3 and being introducedtogether with the feed to slop reel 55, The flbrous material which doesnot pass through the silk shaker 89, is shown being delivered by lineII4 to the feed leading to expeller 6|. Likewise the material which doesnot pass through shaker 96, is shown merged with the flow through lineII4, by way of line II6.

Silk shakers 19 and 89, in addition to treating the underflow fromcentrifuges I and 2,, also preferably use a certain amount of overflowmaterial from centrifuge 3, diverted from line 91I as wash water for theslop contained in the under- Thus line II1 represents diversion ofoverflow from line 9I, through the shaker screen 19, the resultingflltrate being introduced into the underflow line 18. Likewise line II8indicates diversion of overflow from line 9| to the silk shaker 89, withthe resulting filtrate being introduced into the underflow line 88. Withrespect to the silk shaker 96, line II9 indicates diversion of a part ofthe flitrate from the filtering system 91, to the silk shaker, with theresulting filtrate being introduced into the underflow line 94. Fig. 6illustrates diagrammatically a suitable arrangement of one of the silkshaker systems, in this case the shaker 96. From this view it will benoted that the filtrate resulting from treatment of the underflow 94, ismaintained separate from the filtrate resulting from treatment of theliquor flow from line I I9.

heaters may be employed if desired, where a more elevated temperaturewill give good results, al-

though because the passage of the starch through the centrifuge systemis relatively rapid, a relatively small amount of heat loss occurs, andfor that reason heating to the extent indicated gives good results.

Before describing the general mode of operation of my process, asrepresented by the flow sheet of Fig. 1, I shall first briefly describea suitable type of centrifuge which can be utilized. Thus referring toFigs. 3 to inclusive the centrifuge illustrated therein consists of ahousing indicated generally at I36, within which there is a rotatingstructure I31. Structure I31 is formed to provide a centrifuge chamberI38, adapted to receive a fluid feed material, and which is also adaptedfor the simpler discharge of a centrifugally separated underflow andoverflow. Formanufacturing convenience, structure I31 is formed of aplurality of parts, part I39 forming the lower part of the structure,another annular part I4I which is secured to part I39 by ring I42, andan upper conical part I43 which is secured to part MI by means of athreaded engagement, The entire structure I31'is mounted on the lowerend of a drive shaft I44, the upper end of this shaft being suppliedwith a drive pulley- I46 and being. supported by suitable bearing I41. 1

, chamber I38, tubular nozzles I49 are provided at circumferentiallyspaced points on the sides of the wall parts I39. These nozzles I49 havedischargeorifices I5I directed backwardly with respect to the directionof rotation of structure I31.

charged over an annularwier I52, formed at the lower end of part I 39. Y

For a proper understanding of the provision for? I introducing feedmaterial into thecentrifuge chamber; it will be necessary to describe,the

structure interposed below the lower end of shaft I44 and the outerportion of structure I31. It will be noted that part MI is provided withan inner hub I53 which surrounds the lower end of shaft I44. Interposedbetween shaft I44 and hub I53, are the interfltting sleeves I54 and I56,which have a slight amount of play between them. Sleeve I56 is securedto shaft I44 by a threaded connection I51. The lower side of hub I53 isprovided with a counterbore I58 to accommodate an annular shoulder I59formed on the 3 lower end of sleeve I54. The lower end of sleeve I56 islikewise provided with an annular shoulder I6I and interposed betweenshoulders I59 and I6I there is a slip ring I62. Cap I63 is threaded intocounterbore I58 and interposed between this cap and the lower end ofsleeve I56, there is a compression spring I64. Compression spring I64serves to urge shoulders I59 and I6I together upon the faces of ring I62so 'as to form a universal joint.

Depending from hub portion I53 there is an inverted, truncated, conicalsection I I6,into which feed material is adapted to be introduced aswill be presently explained. The upper part of section I66 formstogether with hub I53, an annular feed chamber I61. From feed chamberl61 the feed material is delivered into centrifuge chamber I38, throughtwo difierent sets of ports or ducts. One set of ducts I68 is spacedcircumferentially and is inclined upwardly and outwardly. Another set ofducts I69 is likewise spaced circumferentially, but staggered withrespect to ducts I68 and inclined downwardly and and outwardly bydeflector I12 and is discharged the centrifuge chamber through theorifice In order to cause all of the feed material discharged throughannular oriflce I14 and ducts I68 to flow outwardly and downwardlytowards the periphery of the centrifuge chamber along a conical surface,there is a truncated conical wall portion I16which may be integral'withhub F53 and-part MI. The outer edge I11 of portlon l16 is so disposed asto form an annular opening I18 through which material must flow asit'passes through the chamber by centrifugal force. Wall portion I16therefore in effect divides the centrifuge chamber into two portions I19and I8I, the portion I8I being in direct communication with thedischarge nozzles I49. Chamber portion I9I is also in communication withan upper auxiliary feed chamber I82, through downwardly and out wardlyinclined passages I83, separated by webs The overflowythat is thelighter centrifugally separated material, is adapted to be -dis- H I rcharged I I2 and from this compartment terial in feed chamber "I82,vanes I88 are provided, which can be suitably mounted upon the upperface of hub I53.

To aid in effecting efiicient separation, a plurality of spaced conicaldiscs I81 are disposed within the chamber portion I18, and concentric tothe axis of shaft I44,

To properly understand the manner in which feed material is introducedinto the rotating structure I31 and the centrifuge chamber, how theunderfiow and overflow discharges are handled after their delivery, andhow a portion of the underfiow is returned by way of the auxiliary feedchamber I82, it is necessary to describe the structure of housing I36.This-housing is shown formed of a pluralit of separable sections, thesections being numbered I88, I8I, I82, and I83, and which are securedtogether by suitable means such as bolts. Section I.88 forms a base orsupport, sections I8I and I82 form a volute for receiving the underfiowand for effecting a return of a portion thereof back into the auxiliaryfeed chamber I82, while section I83 servesto support the journal I41 ofshaft I44. The volute formed by sections I8I and I82 includes an annularchamber I84 which surrounds the discharge nozzles I48. It also includespassages I88 extending upwardly and inwardly and whichare separated bywebs I91. The upper ends of passages I88 communicate with the upper endof a depending duct I 88, the lower end of which is disposed within theauxiliary chamber I82.

Referrin to Fig. 4, a portion of the underfiow discharge into annularchamber I84 can be diverted from the apparatus through a port 28I and amanually adjustable valve 282. The particular asaaov'r material can beremoved through opening 22L Extending upwardly fromthe center of thereceiving vessel 288 and within the inner compartment 2 I2, there is aconduit222 which, when the receiving vessel 288 is in normal position,has

its upper end extending into the lower end of conical portion I86 Feedmaterial is introduced into conduit 222 by way of pipe 223. n spill offeed material is caught by the inner compartment 212 and can be removedby way of opening 224.

The machine described above has been diagrammatically illustrated inFig. '1 to clarify the method involved when the machine is utilized inthe present process. Line B in this figure represents introduction ofstarch bearing liquor into the machine. Line 0 represents the glutenoverflow, while line D represents an underflow consisting largely ofstarch particles. portion of the underfiow, designated by letter E, isremoved for final delivery. The remaining portion indicated by letter -Ais being returned back into the centrifuge. Line F indicatesintroduction of wash liquor, into the return circuit A.

To compare Fig. 7 with the actual machine of Fig. 3, line B of Fig. '1is representative of conduit 222 of Fig. 3. Line C of Fig. 7 isrepresentative of the discharge of lighter separated maform of valve282jiilustrated consists of a sleeve I 283 forming a cylinder adapted toreceive the sliding valve plug 284. Valve plug 284 can be adjusted byturning stem 288, to more or less restrict fiow of material through thevalve. Also communicating with passages I88, there is a pipe 281 wherebyadditional fluid material-can be intermixed together with a portion ofthe underfiow for return to the auxiliary chamber I82.

Disposed within the lower housing section I88 there last receivingvessel 288 formed to provide a plurality of annular compartments 288,2and 2I2. To-facilitate attachment and removal of this receiving vessel,means is provided such as shown in Fig. 5. In this case the upper edgeof the outer wall of receiving vessel 288 is provided with a stem 2l5adapted to be engaged by cam member 2I3. Cam member 2 I3 is mounted up nhousing section I88 so that the upper edge of the receiving vessel canbe tightly engaged with a sealing ring 2". The outer receiving vesselcompartment 288 is adapted to receive underflow materlal flowing throughvalve 282, and from this.

compartment material can be removed through an on w opening 2 I8. Theinner compartment ves the overflow material being disterial over wierI52 of Fig. 3. Line D of Fig. 'l is representative of the discharge ofthe underfiow of heavier separated material from the orifices I5I ofFig. 3. Final delivery indicated by letter E in Fig. '1 is by way ofport 28I and the manually controlled valve illustrated in Fig. 4. Thereturn A of Fig. '1 is representative of annular chamber I84, passagesI88 and depending conduit I88 of Fig. 3.

Referring now to the flow sheet of Fig. 1, it will be noted thatcentrifuges I to 4 inclusive are for convenience shown in invertedpositions compared to the representation of Fig. 1, and that theunderflow has been illustrated being discharged from, both sides of themachine. one being for'final delivery, and the other for-the returncircuit. Comparing centrifuge 2 particularly with Fig. 7, introductionof Buhr mill starch by way of line 88, corresponds .to the feed B inFig. 7. Introduction of wash liquor by way of line I81 corresponds toline F. Theunderfiow diverted from the centrifuge 2 by way ofJlne 88,corresponds to line E of Fig. '1, while the return circuit is designatedby letter A in both figures. Assuming that the machine describedindetail with respect to Figs. 3 to 5 inclusive is utilized for thecentrifuge 2 of Fig. 1, Buhr mill starch. containing considerable finefiber, is continuously fed through conduit 222, from the upper end ofwhich it is continuously introduced into the inverted conical portionI88. As the mill starch moves upwardly through'the interior of portionJ88; by virtue of centrifugal force, a preliminary classification takesplace. From this prelimiv nary "classification the heavier classified.of the Buhr mill starch is discharged f chamber I88 through conduit I88upon the inner surface of the conical portion I18. The lightercomponents resulting from the preliminary classification fiow throughconduit HI and I88 through towards-the periphery of the centrifugechamber and through-the orifice 118. The lighter cenu-uugauy separatedmaterial consisting largely A controlled of gluten, togetherv withfine-fiber, flows toward the center of rotation, and discharges overwier I52. The underflow consisting principally of starch particlestogether with water, discharges continually through nozzles I49, and byvirtue of the kinetic energy of the discharge, a portion of thisunderflow is caused to flow upwardly and inwardly through passages I96,and to be redelivered into the auxiliary feed chamber I82. The remainderof the underflow is diverted through valve 202 to the outer receivingvessel compartment 209, for final delivery. That portion of theunderflow which is returned to the auxiliary chamber I82 fiows outwardlythrough passages I83 and is discharged into the outer portion I8I Washliquor is con- This nozzles I49 with discharge particles, but part of itis caused to counterfiow through the chamber portion I19, to bedischarged from the rotor wash liquor intermixes with the underflowbeing returned into the centrifuge by way of. passages I96 and islikewise delivered together with this returned underflow into portion I8I of the cen-- trifuge chamber.

In operating the centrifuge for a proper separation between starch, andgluten together with fine fiber, for a given rate of Buhr mill starchfeed, the rate of return of underflow is considerably greater than therate with which a portion of the underflow is diverted for finaldelivery. A ratio which has given good results for a centrifuge havingan inside bowl diameter of about ten inches and revolving at about 5400revolutions per minute, is about 10 to 1, that is the rate of return ofunderflow discharged from the nozzles is about I times greater than therate of removal of underflow for final delivery. Certain peculiareffects occur when the centrifuge machine described herein, is operatedupon Buhr mill starch in the manner just described. One effect is that ascrubbing action of the starch particles in the underflow takes place,as this underflow passes through nozzles I49 and orifices II. Thisscrubbing action occurs because the flow of material is at relativelyhigh velocity, due to the use of a relatively high speed of rotation forthe centrifuge rotor. High velocity flow through nozzles I 49, andorifices I5I, necessarily sets up violent turbulence within the streamof material, and this turbulence causes a scrubbing of the starchparticles. It has been found that this scrubbing action plays a materialpart in securing proper separating action, as it tends to free thestarch particles of films of colloidal material, such as gluten.

A scrubbing action also takes place in another part of the machine,namely, in the centrifuge chamber portion I8I, adjacent the inlets tothe nozzles I49. Scrubbing action in this region is likewise caused byturbulene or violent agitation. Such turbulence or violent agitationresults from an exchange in energy between the material returned intothe centrifuge chamber by way of auxiliary feed chamber I82, and thematerial separated from the Buhr mill starch which flows into chamberportion I8I through annular ori fice I18. Agitation within chamberportion I8I not only serves the usefu1 purpose of scrubbing separatedstarch particles, but also serves to scour out the adjacent surfaces ofthe rotor, to

prevent clogging of nozzles I49 and to prevent accumulations of solidmaterials. The rate of return of the underflow discharge adjusts itselfin response to the starch discharge in such a manner that'the additionalwash liquor introduced by way of pipe 201 (line F in Fig. '1 and lineI01 in Fig. 1) does not all discharge through together with theseparated gluten and fine fiber over wier I52. This counterfiow of washliquor likewise serves several useful purposes. it is mixed with theunderflow and introduced into centrifuge chamber portion I8I, its flowinwardly through centrifuge chamber I19 causes this liquid to carry withit a certain amount of gluten and solubles scrubbed from the starchparticles in centrifuge portion IOI without diluting the underflow.Likewise the counterfiow of the wash liquor through centrifuge portionI19 assists in effecting separation between the starch and gluten of theBuhr mill starch feed. If desired the amount of wash liquor can be soadjusted as to tend to produce a quiescent zone of separation within therotor. Such a method has been described and claimed in Patent No.1,945,786.

A peculiar effect upon the centrifugal separation, is caused by thepresence of fine fiber in the Buhr mill starch. It has been found thatwhen this fiber is present in the feed to the centrifuge, a moreeffective separation takes place between the starch particles and thegluten. It

is because of the counterflow effect within thezone of separation, thatthe fiber is separated from the starch particles and delivered from thecentrifuge together with the gluten overflow. According to myobservations the relative movement between the fine fiber and the starchparticles, causes the presence of the fine fiber to be effectiv insecuring more efficient separation. Apparently there is a mechanicalwiping action, that is the fine fiber wipes the starch particles toassist in removing adhering fihns of gluten.

Centrifuge I operates in substantially the same manner as centrifuge 2,except that it is fed with grit starch from line 28, in place of Buhrmill starch. In this case the feed contains some fine slop in additionto a comparatively greater amount of coarse slop. Centrifuges 3 and 4likewise operate in substantially the-same manner as centrifuge 2.However as previously stated the chief function of these lattercentrifuges is to effect further washing of the starch underflow fromcentrifuges 'I and 2, after fibrous material has been removed by thesilk shakers 19 and 89. Thus fine fiber does not enter into theseparating action in centrifuges 3 and 4, although more effectivewashing of the. starch particles is made possible by scrubbing, as hasbeen previously described.

It is believed that operation of the process as a whole will be evidentfrom the above description with respect to the flow sheet of Fig. 1, andwith respect to the centrifuges utilized. In general the process may becarried out continuously, although materials may be stored at variouspoints if desired. The various apparatuses indicated in the flow sheetcan of course be operated singly or in multiples, depending upon theplant capacity required, and depending upon conditions encountered inpractice.

' Certain desirable characteristics of my process are as follows:possible, because of the effective separation between starch and gluten,and likewise the resulting starch product is of relatively high purity.A relatively small amount of fresh water is required for carrying outthe process, in addition to that introduced into the steep system,because of the elimination of tabling methods, and because of the mannerin which various available liquors at Because A high yield of starch ismade different points in my process are utilized. An attribute ofconsiderable importance from the standpoint of plant installation andmaintenance,

is the fact that arelatively small number of silk shakers are utilized,compared to prior conventional practice. This is due to the fact thatfine fiber is not removed from the starch fiow, before centrifuging toeffect the major separation between the starch and gluten. Since themajor portion of the fine fiber is delivered together with the gluten inthe overfiows from centrifuges 2, makes possible more eificientseparation of they starch.

It is desirable at this point to amplify upon the nature of fibrousmatter present in starch bearing material, to enable a betterunderstanding as to why less silk is necessary in my method. In additionto the germ, there are roughly speaking,

two kinds of fibrous matter encountered in the manufacture of cornstarch; the so-called coarse slop and the so-called "fine slop. Whilethese two substances may be similar chemically, they have decidedlydifferent physical characteristics. In present day corn starchmanufacture, the coarse slop is removed on copper screens and the fineslop on silk screens. The copper screens are not effective in removingall of the coarse slop, because a certain amount of the smaller sizecoarse slop passes through the perforationsand travels with the starchand the remainder of the fibrous matter. Likewise a certain amount ofthe fine fibrous matter, that is the fine slop, is removed tcgether withthe coarse slop because it is enmeshed together withjthe coarse fibrousmaterial when traveling over the copper screens. It has also been notedthat the percentage of fine slop increases after treatment in a Buhrmill, due to the grinding action upon thefiber. Even after screening andtabling as it has been practiced in the past, traces of fiber inaddition to accidental impurities, remain in the starch, and these arefrequently removed on so-called proving screens, which are screenscovered with extra fine silk.

In addition to distinguishing generally between coarse and fine slops,it is possible to make a distinction between large size coarse slop,small size coarse slop, and true fine slop. The true 'fine slop hasdecidedly different classifying characteristics than the large and smallsize coarse slop, and apparently comes from a different part of the cornkernel. The fine slop as it is commonly removed in prior cornstarchmanufacturing methods, consists mainly of true fine slop, to-

. gether with a certain amount of small size coarse slop. I It is thistrue fine slop which is extremely difilcult to efiectivelyremove by silkscreens. It tends to clog the pores of thescreens, and thus makesnecessary a comparatively large area of silk to secure proper capacity.On the other hand small size coarse slop is fairly easily removed onsilk screens.

It has been previously explained that in operation of centrifuges I and2, a portion of the fibrous material is discharged together with thegluten overflow. This fibrous material discharged together with thegluten overflow is the true fine slop, referred to above. What actuallyhappens is that a separation takes place within the centrifuges I and 2,between the true fine slop, and large and small sized coarse slop, inaddition to the" centrifugal separation between the starch and gluten.Sincein my method the silk screens act only upon the underfiow fromcentrifuges" I and 2, which is free of the truefine slop, it is apparentwhy a considerably less amount of silk is required, and why the removalof fibrous material from the starch is materially facilitated.

The action of the first centrifuging stage upon the fine slop causes aclassification of the fine slop fiber into two portions, one passing outin the overflow and the other passing out in the underfiow, That portionappearing in the overfiow tends to be of-afilamentary nature and incontrast with the more flake-like fiber-remaining in the underfiow it issomewhat more difilcult to remove by silk screening. Irrespective of theprecise character of the fiber appearing in the overflow and underfiowsthe process eliminates a substantial proportion of the fine fiber byseparating it from'the starch and discharging it with thegluten; thusleaving a greatly reduced amount of fiber with thestarch for removal byffine screening.

It is of course possibl to utilize an arrangement of centrifuges such ashas been-described, where the milling system produces only Buhr millstarch from which finefiber has not been removed. However, it isdesirable to centrifuge a relatively high gravity grit starch for thereason that the load upon the Buhr mills and slop reels is therebyconsiderably reduced, with resultant simplification of this portion ofthe equipment utilized.

With respect to the connections between the centrifuges, it has beenpreviously Pointed out that wash liquor is introduced into eachcentrifuge together with the returned portion of the underfiow, so thatwash liquor is delivered from the centrifuge together with the overfiow.In this connection it should be noted that th quan tity of water in thewash liquor should exceed the quantity of the water discharged from themachine in the underfiow. The excess wash liquor which is needed to passout with the overfiow of centrifuge 4 is obtained from the filtrate oi!the filter system Ill. It is for this reason that fiow line III has beenshown in Fig. 1, to divert filtrate from line I IN, to centrifug 4."Because a part of the filtrate from fiow line I04 is diverted I tocentrifuge 4, a like amount is diverted from line 93, representing theoverflow from centrifuge 4, to supply wash liquor for centrifuge 3. Thisdiversion is represented in the fiow sheet by line I09. As has beenpreviously explained, the overfiow from centrifuge 3 serves as'a washfor the germ and slop reels and because this overflow is robbed for theexcess wash liquor for centrifuges I and'2 (line I08) a like amount ofoverfiow from centrifuge I is added to the overflow from centrifuge 3 tomake up for this deficiency.

. It will be noted from the fiow sheet of Fig. 1 that the compensationfor this makeup in turn is represented by fiow line 14 and is drawn fromth overflow of centrifuge I. f

Attention is also directed to the manner in which excess overflow istaken from centrifuge I. It has been found that if material of thisoverfio'w is permitted to be substantially quiescent, the gluten almostimmediately rises to the surface, ,and by drawing offexcess liquor belowthis cloud of gluten, a comparatively clear liquid is obtained, suitablefor washing operations in the wet starch milling system. Such anarrangement affords a rapid and convenient method of obtaining suchliquid. Separator 68, which may be similar to a standard germ separatorexcept that it is somewhat shortened, performs this function upon theoverflow from centrifuge I. It should be noted that the amount of liquordrawn ofl at separator 68 and delivered to the germ washing system onlycompensates for the excess amount of water sent to centrifuges I and 2,over the underflow drawn off these centrifuges. In addition to the abovediscussion concerning the manner in which wash liquors are handled in mysystem, I wish to point out a general distinction between my inventionand the prior art. It will be noted that the wash water which is beingintroduced by way of line IIII, and which augments the moisture in thesteeped corn to deliver the mill starch to centrifuges I and 2, is usedfirst to wash the small size coarse slop in screens 13 and 89, afterwhich it is diverted by Way of line II3 to wash the large size coarseslop. This manner of countercurrent Washing makes it possible to givethe coarse slop a thorough washing without returning any gluten oroverflow water to the milling process for washing purposes, withexception of the water absorbed by the steeped corn. Thus the majorityof the water introduced into the steeping apparatus 9 from settler II,is made up of water introduced by way of line IIlI.

,In actual tests of my process, utilizing centrifuges of the classdescribed,'the percentage of starch in the gluten'overflow from thecentrifuges I and 2 has been recorded below 12%. This compares favorablywith 30% starch in the gluten and 20% starch in th fine slop, which iscon-.

sidered good results with processes heretofore practiced. Such favorableresults can be obfresh water, because the washing of the true fine slopis obviated entirely; and'because the small size coarse slop is washedin the same liquid in which it was carried out of the centrifuges I and2. In this connection note particularly the arrangement of silk shakersI9 and 89, which makes available practically unlimited quantities ofwater for washing the small size coarse slop.

A modification of my process is illustrated in the flow sheet of Fig. 2.In this case no water is drawn off the overflow from centrifuge I foruse in the milling system, but extra water for enabling an increase inthe gravity of the feed to centrifuge 2 and in order toobtaincompensating wash water for the excess overflow in cen-' trifugesI and 2, is obtained by installing a filter in the Buhr mill starch line56. Thus a filter 23I .is shown introducedinto the Buhr mill starch'tained without the use of excessive quantities of line 56, and thefiltrate from this filter is shown being diverted into the overflow lineI 06 from centrifuge 4 by way of line 232. A certain amount of thisfiltrate can also be drawn off by starch line 56.

It has been pointed out that in the method of Fig. 1 an excess ofoverflow is obtained from certain of the centrifuges without increasingthe H. In Fig. 2 the excess overflow is obtainedfliy directing part ofthe filtrate from filter 23I to line I06, by way of-line 232a. Theamount pass- .ing through line I08 in this case compensates only for theamount passed through line I09.

Aside from the particular routing of wash liquors shown for thecentrifuge system in Figs. 1 and 2, it will be apparent that thisparticular systern Or method involves the use of a plurality ofcentrifuges in counterflow series with the underflow pass from one stageas a feed to the next stage. Filtrate from the filter operation 91 isused as a wash in a preceding centrifuge stage, and fresh waterisintroduced into the last stage. The counterflo'w arrangement of thecentrifuges results in eflective separation of starch from gluten andsolubles, and gluten and solubles are concentrated in the overflow fromthe first stage.

Figs. '7 to 14 inclusive show additional embodiments of my process. Inthese figures the dotted, dot dash, and solid line conventions as usedin Figs. 1 and 2, have not been followed, and the diagrammatic showingof the centrifuges'and other parts of the system have been simplified.

Referring first to the process represented by Fig. 8, the material inthe conventional steeps 3Ill is delivered to a wet milling systemrepresented by the grit system 3'IIa and the slop system 3Ilb. Theconventional Buhr mill 3l2 serves to grind the material passing to theslop system for further treatment. The grit system 3I Ia may'followconventional practice, and the grit starch stream 3I3 drawn off the sameis shown being delivered to the tables 3 for primary separation betweenstarch and gluten. The slop system 3| Ib departs from conventionalpractice in that the silk screens which are generally employed for theremoval of fine slop are omitted. Thus the draw-off 3I5 ofstarch-bearing liquor from this system includes all of the materialpassing through the usual copper screens for the removal of coarse slop,and therefore contains the fine slop which otherwise would have beenwashed and removed on silk screens.

The draw-ofl 3I5 is shown being treated upon a silk screen 3 I 6, whichcan be presumed as representative of the first silk screen or stage ofscreens such as are employed in a complete flne slop system. and whichis commonly referred to as drain silk. The tailings 3I'l from silkscreen 3I6, which,

according to prior practice are repeatedly treated to the centrifugerotor, and line 320 indicates introduction of a wash liquor forsupplying liquid for the underflow. The troublesome filamentary sloppasses out with the overflow 3I9 and the remainder of the slop passesout with the underflow 321. At the same time a substantial separationtakes place between the starch and the gluten, whereby the gluten passesout with the overflow 3I9 and starch particles are carried out in theunderflow 32I. The underflow 32I is now treated upon the silk screens323 and 326 for the removal of the remaining fine slop. Tailings fromscreen 323 are shown beingpassed to i need not be described .in detail.

oif cycle is indicated diagrammatically at 334,

the screen 326, and the final tailings 321 from screen 326 are shownbeing delivered back tothe slop system 3| lb where they may beintroducedinto the slop expeiler or the filters. Line 326 represents use ofmaterial passing through screen 326 as 'a wash upon screen 323, and thestarch-bearing liquor from screen 323 is shown being'removed by line326. Wash for screen 326 is shown being suppliedthrough line Thestarch-bearing material passing through silk screen 3| 6, represented byline. 332, is shown being. merged with the how through line 323, ,to

forma Buhr mill starchflow 333 to the table 3l4'.

The tabling may follow conventional practice and A starch flushmay alsosupply wash 320 to, the centrifuge 3 l 8. A

part of the wet side filtrate, represented by line 3, can be returned tothe slop system 3i lb, to be used as a wash on the'co'pper screens.

The overflow 3l9 of centrifuge 3l6, which contains the gluten, can bemerged with the gluten flow line 342 from tables 3 and delivered togluten dewatering apparatus 343. As' indicated by lines 344 and 346, apart of the liquor drawn off from the gluten in apparatus 343 can bereturned to the steeps 3| Ii, and another part to the grit system 3ilatobe usedasa wash.

Operation of the process shown in Fig. 8 will be evident from the abovedescription. The t iiings from screen 3l6 are subjected toclassification in centrifuge 3", and the troublesome flla-,

mentary slop, together with gluten, passes out in the overflow 3l3.Treatment upon silk screens 323 and 32 6 serves to remove the remainingfine slop, and the starch-bearing liquor passin through these screens,together with the starch flow 332 from screen 3l6, merges with the gritstarch stream for tabling.

Fig. 9 shows anotherembodiment employing centrifuging in place oftabling as in Fig. 8; In this case the grit starch stream 3l3 is fed tothe centrifuge 348, representedas being of the type disclosed in LettersPatent Nos. 1,923,454 and 1,945,786. Gluten from the starch stream 3l3passes out in the overflow 343, and separated starch in the underfiow35l. Line 352 represents a continuous return of a major part of theunderflow back into the centrifuge rotor. The starch-bearing liquorpassing through silk screen 3l6 is also shown treated in a centrifuge353, the overflow 354 from which may merge with the overflow 346, to bedelivered to the gluten dewatering apparatus 356. The starch underflowand the return circuit for centrifuge 353 are indicated at 351 and 356respectively. Both of the underflow streams 35l and 351 are shown beingmerged to form in part a feed for the further centrifuge 353. Thetailings from screen 3l6 are supplied in the feed to the centrifuge 3| 6for classification,

part as a wash upon screens 323 and 326, and

part returned back to the slop systemfllb to serve as wash upon thecopper screens. The starch-bearing liquor passing through screens 323and 326 can be merged with the underfiows from centrifuges 346 and353,thus providing a properly diluted feed to the centrifuge 356. The.werfiow 3l3 fromcentrli'uge Ill canbc delivered through a separategluten dewatering apparatus 362, with the water removed in thisapparatusbeing returned for prior operations such as the slop system 3llb.- Thestarch underi'iow 363 1 from centrifuge 356 is shown being delivered tothe starch 'filter 364, where the starch is sub-- .iectedto washing withfresh water. In order'to supply all of the centrifuges with wash liquor,

wet side filtrate 366 from-the filter 364 has been shown routed forintroduction into the return circuit of centrifuges 343, 353 and 3l'8.Similarly,

dry side filtrate m is shown being introduced as a wash into thecentrifuge 356. with respect I to the use of wash liquor in thecentrifuges 346,

353 and 3l6, I prefer to provide an amount of wash which issubstantially suflicient to provide liquid for carrying. out starch inthe respective underfiows. In the centrifuge 353, however, a somewhatgreater quantity of wash is introduced, to provide an excess over thatrequired for carrying out starch in the underfiow 363,

the excess flowing counter-currently through I the centrifuge rotor, andbeing discharged with and the underfiow from the centrifuge is treated Ithus the overflow 36l. more efiicient separation of starch from gluten,

and it is classified in centrifugal separating ap-,

facilitating subsequent filtration and Such operation makes for paratussimultaneously with primary separation slop system: formed by silkscreens (silk screens following the usual Buhr millcopper screens). isomitted. Thus the fibrous material removed in the milling systemis onlycoarse slop,such' as is removed on copper screens, and the mill starchstream 314 contains the fine slop which otherwise. would'have beenremoved by the conventional fine slop system.

The mill starch stream 314 is fed to the centrifuge 316, which may be ofthe type previously described. Lines 311 and 316 from the centrifugerepresent a gluten. overflow and a starch underflow, respectively, andline 313 represents a continuous return of a major part of the underflowback to the centrifuge rotor.

Due to. the classification which takes. place.

in centrifuge 316 (Fig. 10), substantially all of the filamentarysloppasses out with the gluten overflow 311, and'the remaining slop passesout v with the starch underfiow..- The starchunder flow is shown beingdelivered to one or more screens 38l, from which the starch passingthrough the silk is delivered to further treating apparatus, such asthestarch filter 382. As a desirable arrangement, the tailings fromscreen "I can be delivered to additional silk screens 383, and thetailings from the latter can be delivered through line 384 to the slopexpellerpr filter 388 of the milling system. Line 381 indicates deliveryof starch passing through screen 383 to filter 382.

" Wash water for the screens 38| and 383 may be provided from aconvenient source, as for example filtrate from the wet side of filter382.

Thus the filtrate from the wet side, represented by line 388, is shownbeing delivered in part upon the screens 38i and 383, with the remainderbeing returned to the milling system 3. Filtrate from the dry side offilter 382, represented by line 389, is shown being delivered in part asa wash to the return circuit 319 of centrifuge 316 (line 390, with theremainder going to the milling system 3 by line 392.

The gluten overflow 311 is shown being delivered to an apparatus 393,which may consist.

of gluten settlers and filter presses, for effecting removal of water,after which the gluten cake can be delivered tofurther apparatus forfinal drying. At least a part of the water removed by apparatus 393 canbe utilized, if de-- in a conventional fine slop system, is subjected tocentrifugal separation to form the gluten overfiow 311 and the starchunderflow 318. Because of the continuous introduction of wash liquor byline 39l into the return circuit 319, the original liquor carried withthe feed is substantially entirely displaced, so that the wash liquorsupplied serves to carry out starch in the'under fiow 318.Simultaneouslywith the separation between starch and gluten,a'classification of the fine slop occurs, causing the filamentaryslopand slimes to pass out with the glutenoverflow 311. Treatment of thestarch underfiow' on screens 38i and 383 effects removal of the fineslop contained therein, which tails off to the line 384. The screenedstarch passes to the filter 382 for further washing and dewatering.

With a process of this character, as is also true of Figs. 1 and 2, theamount of starch recovered per bushel of corn treated is considerablyhigher than in conventional prior practice, and 1 the quality of therecovered starch is relatively high, with a minimum percentage ofprotein. This is. in part due to more effective washing of the fine slopand to the displacement taking place during separation in centrifuge316, where by solubles contained in the mill starch stream areeffectively passed out with the gluten overfiow 311. Aside from a highquality starch, a high protein gluten is provided which commands apremium price upon the market.

In the above description of FigflO, it has been presumed that the gritstarch system of the general milling system is in conformance withconventional practice, with silk screensbeing utilized in effectingseparation of grits from the grit starch, the grits subsequently beingground and the starch and gluten therefrom merging with the starchdraw-off from the coarse slop system. Fig. 11 illustrates a system inwhich silk from the grit system can be omitted, as well as other silk inthe milling system, and in which all of the starch magmas are mergedtogether for primary separation. In such event, the mill starch stream314 contains not only fine slop which otherwise would have been removedin a conventional fine slop system; but also grits.

After treatment of this feed in the centrifuge 5 316, grits pass outwith the starch in the underfiow 318. In treatment of the starch onscreen 38l, the grits tail off, together with slop, and are subjected togrinding by mill 398. This ground material is then treated upon the silkscreen 383, and the material passing through this screen, consistingmainly of fine starch together with some gluten, is delivered by line391 back to the milling system 3; Utilization of this liquor may be madein the milling system for washing starch stream 314. With such aprocess, 100% elimination of silk screening can be effected in themilling system 3! i, with less washing in the grit system and with aproportionately greater draw-ofiof starch from the same.

In a practical operating process following the general arrangement ofFig. 11, it is desirable to employ" two centrifugesoperating in series,in place of a single centrifugal separating apparatus. Also one may notrequire more than two centrifuge stages, as in Figs. 1 and 2. Such a.modification, in which the silk screens 38I and 383 are inserted betweenthe two centrifuges, is shown in Fig. 12. Thus, the mill starch stream314 from the milling system,3li feeds the first centrifuge 318a, and thestarch underflow from this machine is supplied to the silk screen 38!.After passing through this screen, the starch liquor is supplied to thesecond centrifuge 316b,

by line 398. The starch underfiow take-off from the machine 319-1) isshown delivered to the starch filter 382 by line 399. The dry sidefiltrate from filter 382 can be used as a wash in the i "ntrlfuge 31617,as indicated by Tfienveriiow 402 from centrifuge 31Gb latlfvelyfeiear-liquid and can be used in part y ashflpon screens 38f and 383, and inpart to the milling system 3| i. Thus, line 403 represents delivery of apart of this overfiow to the screens 38! and 383 as a wash, while line404 represents return back to the milling system 3 where it can beutilized for various washing operations. In addition to serving as awash, it is evident that a part of theoverfiow from the secondcentrifuge also serves to dilute the feed to the same. Filtrate from theWet side :of'f1lter 382, which contains a somewhat higher*perohtageof-soliibles than. filtrate from the dry 0 be 'used'gas a washin the first centrifuge ta indicated-by line 406. As previouslydescribed, the fiow rates of feed and wash with respect to the twocentrifuges (Fig. 12) should be adjusted to secure proper operation,with primary separation between starch and gluten and a classificationof the fine slop taking place in centrifuge 318a, and with a secondaryclean-up separation taking place in y centrifuge 31Gb. I In one suitablemethod of operation the rate of introduction of wash liquor intocentrifuge 318a is sufllcient to supply waterremoved with the underfiow318, or even a some- :yhat lesser rate, so that a minor part of theliquid from the feed likewise merges with the underilow. However, in thesecond centrifuge 8161) the wash liquor is introduced at such a ratethat it not only supplies liquid for the underfiow 399, but also causesan upfiow of a certain amount of wash through the centrifuge rotor andthe zone of separation, to merge with the overflow 402. 75 With thearrangement of Fig. 12, in the event purposes, with an eventual merginginto the mill indicated by filter 436 and repulping operation 431, toform the feed 434 to the centrifuge 434a.

silk screens are-omitted from the grit starch system, a mill 3" canoperate upon the tailings from screen 38L to grind the grits separatedthereon. While this may involve a slightly additional amount of glutenin the material passing through screen 383, this factor is onset by thecentrifugal separation to which the material is subjected in centrifugefflb. k

Fig. 13 illustrates a process similar to that of Fig. 12, except that acombined mill starch stream is subjected to partial dewatering beforefeeding the same to'the first centrifuge 31611. To effect suchdew'atering, a suitable continuous filter 408 can be employed, whichoperates upon a part of the mill starch stream. The cake from thisfilter is repulped with the remainder of the mill starch stream, asindicated at 409, to make up a relatively high gravity feed 4| I to thecentrifuge 316a. Filtrate from the filter 408 can be returned to themilling system, as indicated at 2, for re-use in various washing ormilling operations. The ad-- vantage to be gained by such a process isto reduce the volume ofmaterial handled by centrifuge 315a, by virtue ofthe higher gravity feed, thus increasing the capacity of a given, sizeof centrifugal separating apparatus. If desired, all of the mill starchstream can be subjected to filtration and the filter cake repulpedwithanother available liquor.

I1 Fig. 14 shows a simplified process in which starch magmas from thegerm and coarse slop systems are separately centrifuged, as in Figs. 1and 2. In this instance the grit and slop systems are indicated at 415and H6 respectively, with a Buhr mill 4|l or like apparatus operatingupon the starch-bearing material being delivered to. the

slop ,system-4l6 for further screening andwa'shing. It will be presumedin this instance that it is desired to omit all silk screening in themilling system; therefore no silk screens or silk shakers are employedin the grit system 415, and in the slop system 6 the material is treatedonly on copper screens for the removal of coarse slop. The mill starchstream 4 I 8 from the grit and germ removal system is shown beingsubjected to filtering at M9 and repulping at 42l with the remainder ofthe mill starch stream, to eifect dewatering substantially as describedwith respect to Fig. 13. Filtrate 422 is returned to the grit system 415to be used in'washing operations. A mill starch feed 423 of relativelyhigh gravity is delivered to the centrifuge 424a, from which the glutenoverflow 426 and the starch underflow 421 are taken off. The starchunderfiow is treated on the silk screens 428 and 429, the tailings fromwhich are delivered to the feed of Buhr mill 4H by line 43!. Thetailings in this instance consist mainly of grits, together withflake-like slop which may be present.

The material passing through silk'screens 428 and 428 forms the feed forthe second centrifuge 4241), where the starch is subjected to furthercentrifugal separation and washing. The overflow 432 from this secondcentrifuge is used in part as a wash upon silk screens 428 and 423, an ithe remainder is returned to the grit system d '3 for washingoperations. The underflow take-off 433 from the second centrifuge 4241;can be treated to further washing and filtration, as has been previouslydescribed in connection with the other embodiments. Likewise, washliquor, as for example from the finishing starch filter, is supplied tothe centrifuges 424a and 424!) as indicated.

The mill starch stream 434 from the slop sys tem M6 is likewise shownbeing dewatered, as

, used in part as a the bran, yielding a mixture The gluten overflow Ifrom the centrifuge 423a can be merged with the overflow 426 fromcentrifuge 424a and delivered to, dewaterlng means 442. Liquid recoveredfrom. dewatering means 442 can at least in part be returned to thesteeps am, as indicated by line 443. The starch underflow 444 removedfrom centrifuge 439av is shown being treated upon the silk screens 446and 441, from which thematerial passing therethrough is supplied as afeed to the second centrifuge lb. The overflow 448 from centrifuge 4392)can be wash on silk screens 44. and 441, and in part returned back tothe slop system 6 for washing operations. The tailings 44! from silkscreens 446 and 441 consist largely of flake-like fine slop and can bedelivered to the slop expeller or filter 451 of the slop system 4".

The starch underfiow 452 taken off centrifuge 439?; can be treated apartfrom the underflow 433 to effect a separate recovery. Wash liquor' isalso supplied to centrifuges 439a and 43312 from a convenient source, asfor example the filtrates from the starch filter operating upon theunderilow 452. While no great amount of fine slop may be treated incentrifuge 424a, a classification of fine slop occurs in centrifuge439a, to cause the slop of a filamentary nature to pass out in thegluten overflow 4 and the remaining slop to pass out in the underfiow444.

In the utilization of my invention, or of certain features thereof, oneskilled in the art may be expected to make certain changes oradjustments to adapt the process to the equipment available or toprevailing conditions or requirements. The various fiow sheetsillustrated in the drawings are to be taken as diagrammaticrepresentations of the various operations and equipment utilized,leaving a wide latitude of selection and arrangement in makingcommercial installations. For example, where single pieces ofequipmentare indicated, it is evident that two or more pieces ofequipment can be utilized to secure a desired capacity. While aPeltzertype centrifuge, utilizing a continuous return circuit back into therotor, has given good results, a centrifuge of this general type can beemployed without a "return circuit but with an additional supply of washliquor to provide liquid for carrying out starch in the'underfiow. Withrespect to carrying'out silk screening after primary separation betweenstarch and gluten, it should be appreciated that this operation may notfollow immediately after the first centrifugal separation but mayfollowtwo or more centrifuges operating in series or in parallel.

This application is a continuation and consolidation of subject matterdisclosed and claimed in my copending applications Ser. No. 651,701,filed January 14, 1933, and Ser. No. 741,528,1iled September 11, 1934.

I claim:

1. In the process of manufacturing starch from corn including subjectingthe corn in. a com-'- minuted state to separating operations in water toremove the germs and coarse slop, yielding a starch milk containing fineslop; the improvement which comprises centrifuging said starch milk toremove the fine slop therefrom.

2. In the process of manufacturing starch from corn including subjectingthe corn in a comminuted state to separating operations in water toremove the germs and the major portion of of starch, gluten,

, bran from the starch by c residual bran particles and water; theimprovement which comprises remo g the gluten and trifugal force.

3. In the process of manufacturing starch from corn including subjectingthe corn in a comminuted state to separating operations in water toremove the germs and the major portion of the bran, yielding a mixtureof starch, gluten, residual bran particles and water containing cornsolubles; the improvement which comprises removing from the starch bycentrifugal force the gluten, bran and the major portion of saidsolubles.

4. In the process of manufacturing starch from .corn includingsubjecting the corn in a comaaaao'zv I from said separations tocentrifuging operations 7 to remove the gluten and fine slop from thestarch; giving process waters ofzrelatively higher and lower contents ofsolubles; reusing process arating operations to centrifugal force toremove from the starch the gluten and fine slop.

5, In-the process of manufacturing starch from corn including subjectingthe corn in a comminuted state to germ and coarse slop separatingoperations in water: the improvement which otherwise would have beenremoved, subjecting the mill starch to centrifugal separation to form agluten overflow and a starch underflow, thereby causing a classificationof the fine slop to take place simultaneously with the centrifugalseparation whereby filamentary slop passes outwith the gluten overflowand the other part of the slop passes out with the starch underflow, andthen subjecting the starch underflow to screening for the removal ofslop carried therein.

7. In a wet starch manufacturing process utilizing wet millingoperations to produce a mill starch, the improvement comprising omittingfrom the milling operations the conventional fine slop system, wherebythe mill starch stream contains substantially all of the fine slop whichotherwise would have been removed, subjecting the mill starch tocentrifugal separation to form a gluten overflow and a starchunderflowfthereby causing a classification of the flne slopto take placesimultaneously with the centrifugal separation whereby filamentary sloppasses out with the gluten overflow and the other part of the sloppasses out in the starch underflow, subjecting the starch underflow toscreening for the removal of slop carried therein, and introducing awash liquor to the centrifugal separating operation to supply liquid forthe starch underflow.

' 8. In the process of manufacturing starch from corn includingsubjecting the corn in a comminuted state to separating operationsinwater to remove the germs and coarse slop, yielding a starch milkcontaining fine slop; the improvement which comprises subjecting saidstarch milk to a series of centrifuging operations,'in countercurrentarrangement, for removing the fine slop h water having the highersolubles content for steeping corn as the process proceeds; and usingprocess water of lower solubles content at later stages of the process.

10. In a wet starch manufacturing process utilizing wet millingoperations to produce a mill starch, the improvement comprising omittingconventional flne screening from the milling operations for the removalof fine slop, whereby the mill starch stream contains substantially allof the fine slop which otherwise would have been removed, subjecting themill starch to centrifugal separation to form a gluten overflow and astarch underflow, thereby causing a classification of the fine slop totake place simultaneously with the centrifugal separation wherebyfilamentary slop passes'out with the gluten overflow and the other partof the slop passes out in the starch underflow, subjecting. the starchunderflow to fine screening forthe removal of slop carried therein,

subjecting the screened starch to further centrifugal separation therebyforming an overflow and a starch underflow, and utilizing at least apart of said overflow as a wash liquor for said last-mentioned screeningoperation.

11. In a wet starch manufacturing process uti lizing wet millingoperations to produce a mill starch, the improvement comprisingsubstantially omitting from the milling operations the conventional fineslop system, whereby the mill starch stream contains fine slop whichotherwise would have been removed, subjecting the mill the starchunderflow to silk screening for the re moval of slop carried therein,subjecting the screened starch to'further centrifugal separationtherebyforrning an overflow and a starch underflow, introducing washliquor to the last-mentioned centrifugal operation in an amountsufficient to form the liquidin the underflow with an excess for mergingwith the overflow, and

utilizing at least a part of said last-mentionedoverflow as a wash insaid screening operation.

12. In a wet starch manufacturing process utilizing wet millingoperations to produce a mill starch, the improvement comprisingsubstantially omitting from the milling operations the conv entionalfine slop system whereby the mill starch stream contains fine slop whichotherwise would have been removed, subjecting the mill starch stream tocentrifugal separation, thereby forming a gluten overflow and a starchunderflow, supplying a wash liquor to said centrifugal separatingoperation thereby providing liquid for the starch underflow, subjectingthe starch underflow to fine screening, subjecting the screened starchto further centrifugal separation thereby forming anoverflow and astarch underflow,

supplying wash liquor to the second-mentioned centrifugal separatingoperation to supply liquid for the underflow, and utilizing a part ofthe overflow from the last-mentioned centrifugal separating operation asa wash for said flne screening operation.

13. In a wet starch manufacturing process uti-

